Cotton bleaching



Parmesan, 11, 1939 PATENT OFFICE COTTON BLEAOHING Hans 0. Kanfi'mann,

Buflalo, N., Y., assignorto Buflalo Electra-Chemical Company, Inc., Buffalo, N. Y;

No Drawing.

6 Claim.

This invention relates to a method of bleaching cotton and particularly to a method of bleaching cotton wherein the cotton is subjected to a combination treatment with acid hypochlm rite followed by treatment at atmospheric temperature with a minimum of peroxide solution.

This application is a continuation in part of Serial No. 714,735, filed March 8, 1934, now Patent No. 2,107,297, patented February 8, 1938.

In accordance with the procedures of the present invention, cotton goods, particularly goods in the open width, are passed through acidified solutions of hypochlorite, the excess expressed, the goods rinsed and then passed into a bleaching solution containing hydrogen peroxide or material generating the same, the excess solution expressed and the goods permitted to bleach in the damp condition.

An advantage of the procedure of the present invention is to permit the goods to be bleached in open width and this is particularly advantageous where it is desired to bleach certain types of gray goods which can not be piled up in roped form due to the tendency of the production and formation of crease marks in the goods, as, for instance, in collar linings and the like. Another advantage of the present invention is the substantial elimination of all costly apparatus heretofore believed necessary in the bleaching of cotton goods, as, for instance, circulating kiers and the like, since the instant invention provides a method wherein goods may be handled continuously in the open width with excellent and uniform bleaching and wherein the handling of the goods is reduced to a minimum.

The goods may be subjected to a pressure boil, as, for instance, a boil with about 3% caustic soda or other alkali, or this treatment may be omitted and gray goods or unboiled goods may be used, depending upon the type of product desired, that is to say, whether full, white goods are to be produced or goods that are to be subsequently dyed.

The goods, either boiled or unboiled, are passed, generally in open width, although the goods may be used in rope form, continuously through a hypochlorite solution containing from about 0.3 grams to about 4.0 grams active chlorine per liter, although the quantity of chlorine will depend upon the type of goods being treated, the extent to which they are to be treated, as well as the amount of goods passing through the solution. The goods are allowed to remain in contact with the solution for a time suiiicient to saturate the goods with the active hypochlorite, that is to say,

Application February 10, 1937. Serial No.

several seconds to several minutesyalthough the goods may remain in contact for a time up to about ten or fifteen minutes, a time insuflicient to produce tendering of the goods. The goods are then passed out of the active hypochlorite solution, through squeeze rolls .where the excess solution is expressed, then into a rinse bath to remove the last traces of the hypochlorite and then into a bleaching solution containing hydrogen peroxide or equivalent material generating hydrogen peroxide in solution. In general, this solution will contain in addition to hydrogen peroxide some of the following: caustic alkali, soda ash, trisodium phosphate, sodium silicate and other well known alkaline material generally used in the preparation of conventional peroxide bleaching solutions. The quantity of hydrogen peroxide in this bleaching solution, that is to say, the amount of active oxygen therein, is a quantity in general considerably larger than has been employed heretofore in peroxide bleaching solutions employed in the treatment of cotton goods and is, in general, sufficient to produce about a four volume bath, more or less. The goods are merely saturated with the peroxide solution, the excess of the solution being expressed so that the goods may retain from about 50 to 150% of their weight of bleaching solution, the excess of the solution being expressed generally by squeezer rolls. Thereafter, the goods dampened with the bleaching solution, are passed to a storage chamber where evaporation of the solution is prevented and the goods maintained in the damp condition, generally by stacking the goods, and permitted to stand in the damp condition and bleach. In general, the bleaching action requires from about 4 to 18 hours, depending upon the type of goods and the quantity of bleaching solution retained therein, as well as the concentration of peroxide in the solution. After the goods have bleached in the damp condition, they are rinsed and finished thereinafter in any conventional fashion.

The hypochlorite solution is prepared generally by acidifying metal hypochlorites such as sodium or calcium hypochlorite, with an acid, such as sulfuric acid and the pH value thereof adjusted to between about 4.5 and 7, since within these limits inodorous solutions can be prepared and solutions that do not cause irritation upon mucous portions with probable serious illness. The strength of the solution will depend upon the type of goods, the weave thereof, the weight per yard and the amount of bleaching solution to be left in the goods. In general, hypochlorite solutions containing about 0.5 to 4 grams per liter 56 of active chlorine are preferred, although solutions containing greater quantities of active chlorine may be used where the goods are of such quality as not to be damaged or tendered thereby. Where the cotton goods have been given a preliminary caustic boil they are treated with a hypochlorite solution containing considerably lesser quantity of active chlorine than used in treating unboiled or gray goods. 4

After passage through the hypochlorite solution, squeezer rolls and-rinse, the goods are given a steep at atmospheric temperature with a highly concentrated peroxide bleaching solution. The peroxide bleaching solution contains an amount of hydrogen peroxide or sodium peroxide to produce a 4 volume bath or stronger in addition to the conventional alkaline material. The concentration of active oxygen as peroxide, it will be noted, is considerably larger than that used in a solution employed for a peroxide boil. About 50 to 150% of this solution is incorporated in the goods and this is generally efiected by passing the goods into the peroxide solution so that the goods are immersed therein, and the excess bleaching solution expressed by squeeze rolls or removed by centrifugals. The damp goods containing about 50 to 150% by weight of the bleaching solution are then permitted to bleach in the damp condition for a period of about 4 to 20 hours. This is generally done by stacking the goods in a bin or receptacle, thus preventing evaporation and maintaining the 'goods damp, during the bleaching period. The temperature of the bleaching operation is generally about atmospheric temperature, that is to say, temperature of 70-00 F. and not greater than about 120 F. After the'goods have bleached they are rinsed to remove the last traces of peroxide and alkaline material and then finished in any desired fashion.

Example 1 5000 lbs. of cotton piece goods, 4 yards of which weigh approximately one pound, are kier boiled in the well known manner, washed, opened up to the full width and then passed through a solution containing 2 grams active chlorine per liter and having a pH of 5.5. The goods are either stacked for a short period of. time, or are taken immediately to a washer where they are washed free of the remaining active. chlorine. After this treatment the goods are padded to 90% with a 4 volume peroxide solution containing silicate and caustic soda and permitted to steep for hours, then rinsed and finished as desired.

Example 2' 5000 lbs. of cotton piece goods are boiled in the usual manner then washed in the machine, then passed rope form through a solution containing 1 gram active chlorine per liter and having a pH of 5- The goods are then piled up for not more 2 or 3 minutes, for instance by using a jaybox, and are washed out in a washer. The goods are passed through a 4 volume peroxide solution, the excess squeezed out to 90%, taken steeped over night, then rinsed and Example 3 Gray unbleached. go ds are run in the open wldth through a solution containing 4 grams active chlorine per liter and having a pH of 6. The goods are then piled in a container for several minutes and washed in rope form then they are subjected to an alkaline hydrogen peroxide steep for 16 hours, padded 100% with a 5 volume peroxide solution.

From the foregoing it will be seen that the present invention provides a bleaching procedure wherein a minimum of expensive apparatus is chlorite solution having a pH value of between about 4.5. and 7 and thereafter incorporating in the goods sufiicient peroxide bleaching solution containing a high concentration of peroxide to dampen the goods and permitting the goods to steep and bleach in the clamp condition.

3. The method of bleaching cotton goods which comprises passing the goods through a hypochlorite solution having a pH value of between about 4.5 and 7, rinsing the goods, thereafter passing the goods through a bleaching solution containing a high concentration of peroxide, ex-

'having a pH value of between 4.5 and 7, and

thereafter incorporating about 50 to 150% of an alkaline peroxide solution in the goods to dampen the same and thereafter permitting the goods to" bleach in the damp condition.

5. A continuous method of bleaching cotton fibers and goods made therefrom which comprises passing the goods through a hypochlorite solution having a pH value of between about 4.5 and '7. then through a peroxide bleaching solution containing a high concentration of peroxide, eliminating the excess of the peroxide solution from the goods above that required to dampen the goods and thereafter permitting the goods to bleach in the damp condition.

6. A continuous method of bleaching cotton fibers and goods made therefrom which comprises passing the goods through a hypochlorite solution having a pH value of between about 4.5 and 7, rinsing the goods to eliminate unused hypochlorite, then passing the goods through a peroxide bleaching solution containing a high concentration of peroxide, eliminating the excess of the peroxide solution from the goods above that required to dampen the goods and thereafter permitting the goods to bleach in the damp condition.

HANS O. KAUFF'MANN. 

